Suspension bridge



Dec- 1, 1 L. u. E. A. BATICLE' SUSPENS ION BRIDGE Fil ed June 50, 1931 Patented Dec. 1, 1936 UNITED STATES PATENT OFFICE SUSPENSION BRIDGE Louis Urbain Edgar Antonin Baticle, Paris, France 1 Claim.

It is well known that in suspension bridges with parabolic cables the considerable deformations due to movable loads necessitate the addition to the platform of girders providing rigidity. The present invention has for its object means permitting (l) of reducing the deformations of the cables and (2) of obtaining considerable reduction of the girders.

To this end the invention consists in anchoring the main cables at the parts adjacent the piers by means of anchors fixed on the one hand to the cables and on the other at two points located as low as possible adjacent the supports of the cables on the piers on the above stream and below stream sides respectively. This system of anchorage of the main cables can be employed in addition to the anchorage usually employed of the platform adjacent the pillars.

In the accompanying drawing, Figs. 1, 2, and 3 are diagrammatic side elevations of different forms of suspension bridges embodying the invention.

If the diagram of a suspension bridge such as shown in Fig. 1 comprising a platform not provided with girders be considered, it is known that when there is applied at a point M of the cable a load P the cable takes the form BM B which intersects the initial curve at a point Q. It will be seen that by maintaining the part BQ fixed by virtue of the anchors extending from I) such as bI-I", bI-I bl-I, the deformation of the portion of the cable which tends to become lower at both sides of the point M will be considerably reduced.

Calculation shows that for all the loads applied over one-half of the span of the bridge the cable is raised on the side opposite up to one-third of the span. In consequence by anchoring in accordance with the invention a portion of the cable which corresponds to one-third of the span there will be diminished by that extent the effective span of the girder providing rigidity. v

The efiicacy of the anchorage may be improved by giving the anchors a sufficient initial tension so that under the influence of the load on the part of the platform which tends to lower the main cable the reduction in tension (i. e. the compression force which would be produced if the anchors were replaced by rigid thrust members) will be less than the said initial tension. Under these conditions the parts of the cable anchored constitute with their anchors true rigid frameworks, and the central third part of the platform as also the spaces between the points of attachment of the anchors only need be provided with a girder.

The economy of the system will be appreciated if it be considered that the girder is practically equivalent to a straight girder on single supports, the span of which would be between one-third and one-quarter of the effective span.

Fig. 2 of the accompanying drawing illustrates diagrammatically the application of the invention to a suspension bridge having a girder and a platform not anchored, and Fig. 3 the application to the same bridge but with the platform anchored.

In the drawing l indicates the main cable, 2 the girder and 3 the anchors of the cable.

In Fig. 3 where the platform is provided with an anchorage 4, those of the anchors 3 of the cable I which have a great inclination will be advantageously attached to the anchors 4 at their point of intersection 5 therewith. In the absence of the anchorage 4 such inclined anchors will be attached in the same manner to the suspension rods of the platform.

It is to be noted that the essential result of the invention which is the fixity, almost to the state of elastic deformation, of two definite points of the main cable may be attained with any number of anchors without departing from the spirit and scope of the invention.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:

In a suspension bridge of the character described, a plurality of anchorage elements connected at spaced points to the main suspension cables and to the piers below the bridge floor, the points of connection of the anchorage elements secured to each pier being distributed over a distance of approximately one third of the span from the respective piers and connected at a common point to the piers; and all of said anchorage elements being pre-tensioned to such an extent that the maximum overload on the bridge does not overcome the tension, whereby to prevent sagging of the main cable and of the bridge floor under any permissive load.

LOUIS URBAIN EDGAR ANTONIN BATICLE. 

